On the claim for a flood tunnel

Never observed directly, how does the 19th-century claim stand today?
By: John A. Bartram on: Sun 19 of Jun, 2005 [08:01 UTC]

The Oak Island story has incorporated the claim that a flood tunnel once ran from the so-called 'box drains' in Smith's Cove to enter the 'Money Pit' at 110 feet. The claim is not based on direct observation, because none of the treasure hunters, nor anyone else, has ever reported to have seen it; it is based entirely on an assumption made in the 19th century resulting from observed phenomena. Now, in the 21st century and with the benefit of a better understanding of geology and archaeology, a reappraisal of the assumption is long overdue.

The Historical Record

There are no known contemporaneous records for the discovery and excavation of what came to be known as the ‘Money Pit’ (MP) in 1795, or of the excavations by the Onslow Company ca. 1804-05, or that by the Truro Company ca. 1849-50. There is, however, an oral tradition originated by the three discoverers (McInnis, Smith and Vaughan), passed from Vaughan to Lynd of the Onslow Company, then to various others, notably R. Creelman and J.B. McCully? of the Truro Company.

This oral tradition resulted in a number of newspaper pieces starting in 1857 and in more detail in 1862, then in the Prospectus of the Oak island Treasure Company in 1893.

Early Excavations

The first excavation to reach any great depth was that of the Onslow Company. No flood tunnel was observed. At 95 feet, the pit flooded to within 25-30 feet of the top. Bailing did not reduce the water level. The workers did not observe that the water was saline - seawater - even though the act of bailing is, in its nature, a wet experience.

They then dug an auxiliary shaft 14 feet away by and from its bottom at 100 feet, drove a lateral tunnel into the MP. Two feet from the MP, water in the MP entered the side tunnel and flooded the new shaft. Work was abandoned. Again, the water was not observed to be seawater.

The MP was re-excavated in 1849 by the Truro Company and water was reached at 86 feet, at which point the MP was abandoned.

In the summer of 1850, the Truro Company sank a second auxiliary shaft to one hundred and nine feet, ten feet away from the Money Pit. From the bottom of this, at 110 feet, they dug a lateral tunnel into the MP. Again, water burst through and flooded the new shaft.

It must be noted that at this point in time, treasure hunters had created two tunnels, entering the pit at depths of some 100-110 feet. Both were dug from the general direction of Smith's Cove.

Somehow and for reasons that are not consistent, they decided that the water was entering the MP via a flood tunnel running from Smith’s Cove. The minimum length of such a tunnel would be over 500 feet. It is worth noting here that a tunnel to the sea at South Shore would have been less than half that distance and no good reason has been proposed as to what would have made the longer distance the most suitable.

Circa 1861/84 the Oak Island Association used 63 men and 33 horses in a failed attempt to bail out the water. The pit collapsed. Apparently, there was a large empty space just below the 120-foot level.

In 1864, workers believed that they had located the flood tunnel entering the MP at about the 110-foot level. It was reported to be four feet high and two and a half feet wide. Blocking this did not stop the inflow of water.

The suggestion of a flood tunnel entering the pit from the direction of Smith's Cove must now take into consideration the other two tunnels, made by treasure hunters of the two previous expeditions, which we know actually did enter the pit at about the same depth and from the same general direction. As the treasure hunters of 1864 made no reference to these earlier tunnels, it is fair to question whether or not they had knowledge of them. At the same time, one must consider if it is even possible for a 12'-diameter tunnel to sustain three man-sized tunnels entering the pit, from the same general direction, and at the same approximate depth. There is only so much area of surface available; the pit and tunnels were driven through soil, not rock; I conclude from these facts that the suggested third tunnel was not physically possible.

Over many decades, various and numerous attempts made to block the supposed flood tunnel as it entered Smith’s Cove failed to either find the tunnel, or stop the inflow of water.


Belief in the existence of a flood tunnel never had a factual basis and there has never been a good reason to accept this suggestion.

Those who first bailed water from the MP did not observe that it was seawater.

Extensive searching through the 19th and 20th centuries failed to find any evidence of a flood tunnel.

All attempts at blocking the supposed flood tunnel – by both digging and use of explosives - have failed to stop the flow of water into the MP.

There is therefore no reason now to believe that there is a flood tunnel. Those who supposed in 1864 that a flood tunnel entered the MP simply misinterpreted one of the two lateral tunnels dug earlier from an auxiliary shaft.


There is a simple and natural explanation of how water enters the MP.

Bedrock of limestone lies at 160-180 feet and contains numerous faults and voids. Above that are sandy, rocky subsoils to 50-100 feet. The surface soils are composed of firm clay. Graham Harris, civil engineer and co-author of Oak Island and its Lost Treasure, provides this description of the island’s geology:

Geologically the island is a drumlin. Composed almost entirely of dense glacial till, it is a remnant of the last Ice Age. This till overlies anhydrite bedrock, with which is associated some minor limestone. Anhydrite possesses the dubious property of being exceedingly soluble, more so in salt water than in fresh. Paradoxically Oak Island is the only island in the region to be underlain by anhydrite. On the adjacent mainland, and on other islands in the region, sounder limestones and slates can be found at shallow depth.

…digging the first shaft through dense till into the underlying anhydrite is a simple operation fraught with little peril. But once the excavation fills up with water, drawn into it through systemic seepage paths within the anhydrite, these seepage paths will enlarge progressively. The greater the pumping activity the greater the rate of solution of the anhydrite and, of course, the greater the rate of inflow. Once started it is a vicious circle, and one likely to prove catastrophic as the solution passages enlarge.

Treasure-seekers centuries later would repeatedly attempt to dewater the workings by pumping - an exercise as fruitless as trying to pump the Atlantic Ocean dry! In recent years, massive sinkholes have developed offshore showing that the seepage paths radiating outwards from the base of the Money Pit have grown great indeed.

- Recovering the Oak Island Treasure, Graham Harris, C&G Association Journal, Spring 2002.

Richard Joltes, an archaeologist who has studied the Oak Island mystery extensively, states:

What most likely happened on Oak Island was that once the diggers reached a certain depth the pressure exerted by sea water flowing through the channels and fissures in the rock became too great for the earth remaining in the Pit, so a "blow-out" occurred and the Pit was filled as would any hole dug to such a depth in close proximity to a body of water. It must be remembered that the island rises a maximum of thirty feet above sea level, and the Pit was dug to a depth of over 100 feet. Thus, it extended roughly 70 feet below mean sea level a depth at which the remaining soil would be subject to considerable pressure.


Also, the water in the hole is not actually seawater. Instead it is brackish, indicating that a freshwater 'lens' exists on the island, riding atop the surrounding seawater due to the density difference between the two. This is apparently quite common where island geologies are concerned (Aubrey, 2002). If the so-called 'box drains' actually existed we would expect to find only seawater in the Pit. Instead, the findings indicate that a subterranean stream, normal water infiltration through the deeper 'sand and boulder' soils, and/or other natural mechanisms have caused the flooding of the Pit and other shafts.

This finding is reinforced by the results of side-scan sonar studies that were conducted at the same time. No indications of any sort of channel or 'drain' between the Pit area and the shoreline were found. The scientists summarized this finding during the interview by stating that 'no direct connection to the surrounding ocean was found during the study (Gallo, 2002).'

Gordon Fader of the Bedford Institute of Oceanography, Nova Scotia, states:

“I know the bedrock is filled with channels. They were drilled by Blakenship and cameras were lowered in them. The walls of the caverns are sculpted by flowing water - no question.”

In 1995, the Woods Hole Oceanographic Institute (WHOI) introduced an extremely sensitive dye into Borehole 10-X. WHOI scientists then monitored the island’s coastline without detecting any trace of the dye.

A 'Blow-Out'

Those who assumed (originally and now) that the only way the pit could have flooded was via a flood tunnel have a problem in understanding how it could have resulted from a natural process.

It does not take a rocket scientist, if the phrase will be excused, to appreciate that digging the first shaft through dense till into the underlying anhydrite is a simple operation fraught with little peril. But once the excavation fills up with water, drawn into it through systemic seepage paths within the anhydrite, these seepage paths will enlarge progressively.

- Graham Harris, Civil Engineer, specialist in practical soil mechanics applied to large projects mostly in the mining industry, co-author with Les MacPhie? Oak Island and its Lost Treasure

According to this expert, water would have entered the pit by a natural process, from below, through bedrock and soil. What happened when the treasure hunters excavated the pit was more dramatic than seepage.

A mining term indicating a catastrophic event when the external hydrostatic or rock pressure causes a failure of the rock environment in which mining is taking place. The mine workings become inundated with water and debris as a consequence. This type of event often leads to loss of life.

The island's 'Cave-in' pit is an example of how the local geology is susceptible to this type of occurrence. The 'Money Pit' suffered a number of collapses, as it was excavated by treasure hunters.

In 1965, Robert Dunfield, a qualified and experienced geologist, applied modern survey techniques and open-pit mining methods to the island.

He conducted spectrographic tests on the water from the Pit and showed it was coming from the ocean, not from the sea immediately adjacent OI.

When his examination by closed circuit television of his 140-foot shaft failed to show any indication of a flood tunnel, he rode the bucket of an excavator to the bottom to confirm this personally.

His measurements of the inflow of water into the Pit from above 140 feet (only 15 gallons per minute) demonstrated that nearly all the water intake of the Pit was coming from below, not from a flood tunnel above 140 feet.

He conducted dye tests, which failed to disclose a connection to the adjacent sea.

In June 1966 and February 1967, he wrote a number of letters regarding his work on Oak Island and concerning the idea of a flood tunnel stated:

"We resolved the water problem completely beyond a shadow of a doubt. Water enters through a natural course and caves typical to the limestone and gypsum of the Windsor formation."

His final stated position on this matter:

"This deceives the theory of man-made flood tunnels from which water defeated searchers for the past 170 years."


There is no reason today to disagree with Dunfield’s position. Natural, geological processes are responsible for water entering the MP. The accounts of the excavations show every symptom of the phenomenon of successive generations of treasure hunters misinterpreting the works of earlier treasure hunters as being 'original'. This pattern extends beyond the subject here to other features excavated by Oak Island treasure hunters.

Archaeological excavation of the area under the 'Money Pit' and above bedrock requires a method to stop the flow of water into the site. The geology of the area surrounding and beneath the MP needs further geological study in order to understand the movement of material from the MP into areas within the bedrock.

Are there any counter-arguments, in favour of a 'flood tunnel'? As nobody has ever seen a flood tunnel, the only argument in favour of its existence can be the same one used in the 19th century: an assumption based on a poor understanding of the observed phenomena. Such speculation hardly qualifies as an argument. Further, counter-argument to try and expose flaws in the proposal that there is no flood tunnel cannot, by itself, work in favour of a flood tunnel. Those supporting the assumption of a flood tunnel carry the burden of proof, for which no direct evidence has ever existed.

Note: All unquoted material on these pages is © 2005 John A Bartram. All rights reserved. Short excerpts may be used as long as proper credit is given and advance permission is obtained.